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Sally J Aldous, A Mark Richards, Louise Cullen, Martin P Than, In Reply, Clinical Chemistry, Volume 58, Issue 1, 1 January 2012, Pages 313–314, https://doi.org/10.1373/clinchem.2011.176305
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P. Kavsak and A. Jaffe raise some important issues regarding the diagnostic and prognostic utility of change criteria with high-sensitivity troponin assays in patients with acute coronary syndromes (1).
Our recently published study (2) evaluated a cohort of 939 patients presenting with chest pain, with an acute myocardial infarction (AMI)1 rate of 21.3%. In patients with a peak concentration (at 0–2 h) in the Roche high-sensitivity cardiac troponin T (hs-cTnT) assay ≥99th percentile, use of the relative change between 0 h and 2 h after presentation significantly improved the specificity but reduced the sensitivity for the diagnosis of AMI. The authors refer to a recent publication that demonstrated that absolute changes in troponin outperform relative changes between 0 h and 1 h or 2 h after presentation for the diagnosis of AMI (3). The area under the ROC curve (AUC) was 0.95 for absolute changes and 0.76 for relative changes. The AUCs for absolute values (irrespective of the change) were reported for baseline concentrations (0.94 and 0.95 for hs-cTnT and hs-cTnI, respectively) but not peak concentrations for comparison. The ROC curve–determined optimum for absolute change was 0.007 μg/L. An analysis of our study showed that the use of relative changes in the hs-cTnT assay was inferior to the use of absolute changes [AUC, 0.78 (95% CI, 0.75–0.81) vs 0.92 (95% CI, 0.90–0.94); P < 0.001]. The use of absolute changes was inferior to absolute peak values irrespective of change [AUC, 0.95 (95% CI, 0.93–0.97); P = 0.003]. The ROC curve–determined optimum for relative change was 10% and was 0.002 μg/L for absolute change. The respective sensitivities and specificities for AMI for the peak hs-cTnT value ≥99th percentile were: (a) 94.4% (95% CI, 90.7%–96.9%) and 79.8% (95% CI, 78.8%–80.5%) irrespective of change; (b) 69.0% (95% CI, 63.7%–73.8%) and 89.7% (95% CI, 88.3%–91.0%) with a 10% relative change; and (c) 82.0% (95% CI, 77.0%–86.2%) and 91.2% (95% CI, 89.9%–92.3%) with an absolute change of 0.002 μg/L.
